1. Field of the Invention
The present invention relates to a seasoning apparatus and a seasoning method, and more particularly to technology for seasoning a stack of sheets of paper on which printing has been performed using ultraviolet-curable water-based ink.
2. Description of the Related Art
When ink is deposited on a sheet of paper in a printing apparatus, expansion and contraction of the paper sheet occurs immediately after the ink deposition due to differences in the amount of water within the paper sheet resulting from light and dark tones (i.e., difference in deposited volumes) of the ink in the image region in the paper sheet. This problem is especially pronounced in a system that prints onto general printing paper using water-based ink. Moreover, when carrying out double-side printing, normally, after completing printing on one side (a front face) of a paper sheet, printing is subsequently carried out on the reverse side (a rear face) of the paper sheet; however, since there is significant expansion of the paper sheet immediately after the printing on the front face, then a problem arises in that deviation occurs in the sizes and positions of the images printed respectively on the front face and the rear face (i.e., there is mismatch between the front and rear positional registration).
Furthermore, in the case of single-side printing also, and not only double-side printing, there is a problem that the occurrence of cackling (undulation) of the printed paper sheet as a result of the above-described deformation of the paper sheet causes deterioration of printing quality and also causes adverse effects on subsequent processing steps, such as a binding process, which are carried out after the printing step.
In order to prevent these problems, it is necessary to season the paper sheet immediately after printing so as to adapt the paper sheet to the ambient temperature and humidity.
Japanese Patent Application Publication No. 10-297813 discloses technology in which the periphery of a stack of paper sheets is enclosed by side plates and air is blown through at least one air blowing port arranged in the side plate, whereby dispersion of the air blown through the air blowing port to the exterior of the paper stack is prevented, and the air can be caused to flow efficiently in amongst the paper sheets. Japanese Patent Application Publication No. 10-297813 further discloses technology for sucking air between the paper sheets when the air blowing has ended, so as to press down the disordered paper sheets to be stacked in order.
In addition, with conventional thermoplastic ink, image strength is poor and scratches occur during subsequent processing, and the like, and therefore ink that is curable with active light (e.g., ultraviolet (UV)) is desirable. In order to reduce organic solvent in the ink due to environmental considerations, UV-curable water-based ink containing water as a solvent has been developed; however, this entail a problem in that curing of the UV-curable water-based ink does not progress efficiently, due to the presence of water in the ink.
Japanese Patent Application Publication No. 2007-245653 discloses an image forming method in which an image formed from UV-curable water-based ink on a recording medium is irradiated with UV light by a UV light irradiation device, and the method includes a step of blowing a warm air flow onto the image by a warm air flow blowing device, and a subsequent step of curing the ink forming the image by irradiation of UV light of maximum intensity by the UV light irradiation device. In this method, however, if the printing speed is fast, a problem arises in that there is insufficient time to cure the ink forming the image and, although the surface of the printed item is cured, the interior portion thereof cannot be cured adequately.